selftests: mptcp: connect: remove duplicated spaces in TAP output

It is nice to have a visual alignment in the test output to present the
different results, but it makes less sense in the TAP output that is
there for computers.

It sounds then better to remove the duplicated whitespaces in the TAP
output, also because it can cause some issues with TAP parsers expecting
only one space around the directive delimiter (#).

While at it, change the variable name (result_msg) to something more
explicit.

Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240906-net-next-mptcp-ksft-subtest-time-v2-5-31d5ee4f3bdf@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>